Green Treatment and Thermal Characterization of Eucalyptus urograndis Leaves by TG/DTG

According to the Food and Agriculture Organization (FAO), global pulp and paper production reached approximately 700 million tons in 2020. However, this impressive output comes at a cost, generating substantial amounts of lignocellulosic waste, particularly eucalyptus leaves, which are frequently discarded. For every 100 tons of pulp produced, an estimated 48 tons of waste are generated. The high content of organic extractives and lignin in eucalyptus leaves forms a natural barrier that complicates the extraction of nanocellulose, making delignification a crucial step in the process. This study evaluated the efficiency of treatments for obtaining nanocellulose from Eucalyptus urograndis leaves and characterized the resulting material using TG/DTG. Previously ground eucalyptus leaves were treated with NaOH solution (5% m/v), followed by washing protocols to achieve a neutral pH. The three samples then underwent steam explosion through cycles of pressurization and depressurization, followed by Turrax and sonication treatments. The treated samples were characterized by TG/DTG thermal analysis techniques in a TA Instruments Q600 simultaneous analyzer (25 to 600°C, 10 °C/min under N₂). The thermogravimetric curves of all samples showed two main mass loss stages: the first (below 100°C) corresponds to moisture evaporation, and the second (200 to 400°C) corresponds to hemicellulose and cellulose decomposition. The DTG curves exhibited three decomposition peaks around 50°C (moisture loss), 245°C (hemicellulose decomposition), and 305°C (cellulose decomposition). Notably, no lignin decomposition peak was observed, confirming the effectiveness of lignin removal. The results suggest that non-aggressive green treatment with a low alkaline reagent content was efficient in lignin removal, facilitating access to micro- and nanocellulose. This approach promotes the potential of agroforestry residues and supports sustainable applications in areas such as biodegradable packaging, polymeric reinforcements, and advanced biomaterials.